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Blog about skin pathologyFri, 18 Aug 2017 05:09:22 +0000enhourly1http://wordpress.com/https://s2.wp.com/i/buttonw-com.pngskinpathonlinehttps://skinpathonline.wordpress.com
Gram-Twort Special Stain For Bacteria – Method and Tipshttps://skinpathonline.wordpress.com/2011/06/29/gram-twort-special-stain-for-bacteria-%e2%80%93-method-and-tips/
https://skinpathonline.wordpress.com/2011/06/29/gram-twort-special-stain-for-bacteria-%e2%80%93-method-and-tips/#respondWed, 29 Jun 2011 06:44:39 +0000http://skinpathonline.wordpress.com/?p=115]]>The Gram-Twort variation of the standard Gram stain is the most common variant used in histopathology laboratories for the demonstration of Gram-positive and Gram-negative bacteria in formalin-fixed sections.

The standard Gram stain was developed and reported in 1884 by Hans Christian Gram (therefore Gram stain should always be spelt with a capital). He developed the technique to distinguish a certain group of bacteria in lung tissue, but noted that Typhus Bacillus was not visualised. The standard Gram stain works on the premise that the peptidoglycan rich cell wall of Gram-positive bacteria is stained by the crystal violet and the Gram-negative bacteria take up the counterstain.

Below is the author’s method of choice.

Solutions

– Crystal Violet – 0.5% crystal violet in 25% alcohol

– Gram’s iodine – 1g iodine + 2g potassium iodide. Dissolve in a few mls of distilled water. Make up to 300ml with distilled water.

– Well defined dermatoscopic and physical criteria for lesional morphology and histopathological characteristics are available and have increased the accuracy in distinguishing PSCN from Spitz naevi and melanoma.

– An accurate diagnosis is best gained from clinicopathological correlation.

– PSCN typically occurs in young women, only 25% of cases in patients > 30 years old.

– Punch biopsy as initial management is not recommended as misdiagnosis as melanoma is more likely.

]]>https://skinpathonline.wordpress.com/2011/06/23/role-of-genetics-and-sex-steroid-hormones-in-male-androgenetic-alopecia-and-female-pattern-hair-loss-an-update-of-what-we-know/feed/0skinpathonlineGrocott Hexamine-Silver Special Stain For Fungus – Method and Tipshttps://skinpathonline.wordpress.com/2011/06/22/grocott-hexamine-silver-special-stain-for-fungus-%e2%80%93-method-and-tips/
https://skinpathonline.wordpress.com/2011/06/22/grocott-hexamine-silver-special-stain-for-fungus-%e2%80%93-method-and-tips/#commentsWed, 22 Jun 2011 02:10:59 +0000http://skinpathonline.wordpress.com/?p=106]]>The Grocott Hexamine-Silver special stain is the method of choice for a large majority of histopathology laboratories for the demonstration of all fungi. The formalin-fixed sections are exposed to chromic acid which reacts with fungal cell wall polysaccharide components to form chromic acid-aldehydes. These then reduced by a hexamine-silver solution at an alkaline pH. This causes them to be selectively blackened. It should be noted that this method is not specific for fungi but rarely fails to demonstrate any fungi within the test tissue.

7. Treat sections with working hexamine solution (preheated in coplin jar at 56 degrees Celsius) at 56 degrees Celsius for 10-20 minutes. Check control sections to see if fungi are a dark brown colour, if not return to solution checking regularly at 3 minute intervals until correct colour achieved.

– As with all other silver stains wash everything that you are going to use thoroughly with distilled water.

– Store the stock hexamine-silver solution at 4 degrees Celsius away from sunlight. It will keep for 1-2 months. If a white precipitate forms give it a good shake and it should redissolve.

– Do not extend the time in chromic acid too long as this can over oxidize the carbohydrates to carboxylic acid and therefore not take up the silver stain.

– Do not reduce the time in chromic acid as this will lead to under oxidation and therefore no take up of the silver stain.

– The chromic acid can be reused but its efficiency will decrease after each use.

– If the control sections are failing to stain even after extending the staining time in the heated hexamine-silver solution you have more than likely forgotten to add the borax. If so, you can just add it and continue with the stain.

– If you have a large amount of silver precipitate over your sections it is probably due to using low-grade silver.

– If you forget the sodium thiosulphate step you will not realise until after retrieving the slide from storage further in the future, as the remaining silver not removed will react with sunlight turning black.

]]>https://skinpathonline.wordpress.com/2011/06/22/grocott-hexamine-silver-special-stain-for-fungus-%e2%80%93-method-and-tips/feed/2skinpathonlinePerls’ Technique For The Demonstration of Haemosiderin – Method and Tipshttps://skinpathonline.wordpress.com/2011/06/20/perls%e2%80%99-technique-for-the-demonstration-of-haemosiderin-%e2%80%93-method-and-tips/
https://skinpathonline.wordpress.com/2011/06/20/perls%e2%80%99-technique-for-the-demonstration-of-haemosiderin-%e2%80%93-method-and-tips/#commentsMon, 20 Jun 2011 01:09:53 +0000http://skinpathonline.wordpress.com/?p=104]]>Iron is absorbed in the duodenum by cells called enterocytes. It is then stored or combined with a transport protein molecule. This iron-protein complex is then taken to the bone marrow where the iron is incorporated into the substance known as haemoglobin which is involved in oxygen transportation.

Iron can be stored in the bone marrow and spleen in its ferric state (Fe3+) as haemosiderin when combined with protein. When haemoglobin is broken down by tissues this results in the formation of haemosiderin.

When there is excess iron in the body haemosiderin can be found deposited in organs that are involved with iron storage such as the spleen, bone marrow and liver. This condition is known as haemosiderosis.

A condition called haemochromatosis exists where the body indiscriminately absorbs iron resulting in the deposition of copious amounts of haemosiderin in many tissues.

Haemosiderin founds in histology sections is usually derived from the breakdown of damaged erythrocytes and can also be found absorbed by macrophages (siderophages).

The method used by the wide majority of histology laboratories for the demonstration of haemosiderin is the Perls’ technique. This method works by the hydrochloric acid (HCL) splitting off the bound protein which then allows the potassium ferrocyanide to bind with the Fe3+ and form ferric ferrocyanide (Prussian blue).

– Stronger staining results can be found by carrying out step 2 at higher temperatures (e.g. 37-56°C). This can result in false positive results. This author has found room temperature to suffice.

– The washing step (step 3) should not be decreased below 5 minutes as thorough washing is required to prevent a heavy dye precipitate resulting from the neutral red counterstain.

– The author has found neutral red to be the best counterstain. Do not use safranin as this can stain the Prussian blue granules a dark purple colour.

– Always mount in a DPX-type mountant as other mounting media results in fading of the stain.

– A common artefact is the presence of blue granules on and around the section. This can be due to expired HCL or potassium ferrocyanide. It can also be due to iron contaminants in the tap water. This can be fixed by replacing all steps from the cutting of the sections to the mounting of the stained slide that involve tap water with distilled water.

]]>https://skinpathonline.wordpress.com/2011/06/20/perls%e2%80%99-technique-for-the-demonstration-of-haemosiderin-%e2%80%93-method-and-tips/feed/1skinpathonlineModified Ziehl–Neelsen Stain For Leprosy Bacilli – Method and Tipshttps://skinpathonline.wordpress.com/2011/06/13/modified-ziehl%e2%80%93neelsen-stain-for-leprosy-bacilli-%e2%80%93-method-and-tips/
https://skinpathonline.wordpress.com/2011/06/13/modified-ziehl%e2%80%93neelsen-stain-for-leprosy-bacilli-%e2%80%93-method-and-tips/#commentsMon, 13 Jun 2011 02:43:37 +0000http://skinpathonline.wordpress.com/?p=102]]>Leprosy bacilli in comparison with tubercle bacilli are much less acid- and alcohol-fast. The leprosy bacilli’s lipid envelope is also much more affected by the fat solvents traditionally used to dewax sections (i.e. Xylene). Due to these factors a modification on the standard Ziehl-Neelsen technique is used for the demonstration of leprosy bacilli.

]]>https://skinpathonline.wordpress.com/2011/06/13/modified-ziehl%e2%80%93neelsen-stain-for-leprosy-bacilli-%e2%80%93-method-and-tips/feed/3skinpathonlineLack of UV-A Protection In Daily Moisturising Creamshttps://skinpathonline.wordpress.com/2011/06/07/lack-of-uv-a-protection-in-daily-moisturising-creams/
https://skinpathonline.wordpress.com/2011/06/07/lack-of-uv-a-protection-in-daily-moisturising-creams/#respondTue, 07 Jun 2011 10:16:11 +0000http://skinpathonline.wordpress.com/?p=99]]>Came across another interesting article in the May edition of ‘The Archives of Dermatology’ 2011. The article is entitled ‘Lack of UV-A Protection In Daily Moisturising Creams’ on page 618.

Ultraviolet radiation (UV) contains UVA, UVB and UVC subtypes. The major source of UV exposure for humans is sunlight. The earths ozone layer blocks approximately 98% of all UV radiation and the 2% which reaches the earths surface 99% is of the UVA subtype. UVB can cause direct DNA damage whereas UVA causes indirect damage of DNA via the formation of free radicals. Therefore it is important any sunscreen solution contains both UVA and UVB filters.

]]>https://skinpathonline.wordpress.com/2011/06/07/lack-of-uv-a-protection-in-daily-moisturising-creams/feed/0skinpathonlineVerhoeff Van Gieson Elastin Special Stain – Method and Tipshttps://skinpathonline.wordpress.com/2011/06/06/elastin-special-stain-method-and-tips/
https://skinpathonline.wordpress.com/2011/06/06/elastin-special-stain-method-and-tips/#respondMon, 06 Jun 2011 12:03:44 +0000http://skinpathonline.wordpress.com/?p=91]]>Elastin is a connective tissue protein which allows the tissues of the body to return to their original shape after distortion or stretching. Elastin fibres can be of varying size and diameter and are particularly well seen histologically in sites such as the lung, heart, blood vessels and the dermis.

Histological demonstration of elastin fibres (or lack of them) are important in diagnostic pathology for conditions such as arteriosclerosis, temporal arteritis and elastosis. Fine elastic fibres are not so easily seen on standard haemtoxylin and eosin (H+E) staining therefore special stains which demonstrate elastin clearly are vital.

There are many elastin special stain techniques such as Weigert-Type, Orcein, Aldehyde-Fuchsin and Verhoeff’s. The most common is Verhoeff’s technique of staining elastin due to its quick method and strong elastin colour result. Below is the author’s favoured method for demonstrating elastin which is a version of the Verhoeff’s.

]]>https://skinpathonline.wordpress.com/2011/06/06/elastin-special-stain-method-and-tips/feed/0skinpathonlinePersistent Melanocytic Nevi: A Review and Analysis of 205 caseshttps://skinpathonline.wordpress.com/2011/06/01/persistent-melanocytic-nevi-a-review-and-analysis-of-205-cases/
https://skinpathonline.wordpress.com/2011/06/01/persistent-melanocytic-nevi-a-review-and-analysis-of-205-cases/#respondWed, 01 Jun 2011 06:06:58 +0000http://skinpathonline.wordpress.com/?p=88]]>Great article in the June 2011 issue of the ‘Journal of Cutaneous Pathology’ regarding persistent melanocytic naevi. Good reading for those interested in the subject.

Things of note are

– female predominance (reason unclear)

– back is the most common site followed by abdomen then chest

– mean time between original biopsy then biopsy of persistent naevus was 9.7 months

]]>https://skinpathonline.wordpress.com/2011/06/01/persistent-melanocytic-nevi-a-review-and-analysis-of-205-cases/feed/0skinpathonlineMelanoma Research – Sex differences in survival of cutaneous melanoma are age dependenthttps://skinpathonline.wordpress.com/2011/05/31/melanoma-research-sex-differences-in-survival-of-cutaneous-melanoma-are-age-dependent/
https://skinpathonline.wordpress.com/2011/05/31/melanoma-research-sex-differences-in-survival-of-cutaneous-melanoma-are-age-dependent/#respondTue, 31 May 2011 04:08:16 +0000http://skinpathonline.wordpress.com/?p=86]]>Came across an interesting article in the latest issue of the Melanoma Research journal regarding differences in survival rates based on sex. It has been previously observed that women have a better survival rate for melanoma than men. This has also been observed in other cancers such as lung adenocarcinoma and colon cancer.

The study reveals that the slight survival benefit women with melanoma experience, disappears after the age of 60. This is mirrored, but also conflicts with other studies referenced within the article.

Proposed reasons for this female survival benefit include women being more prudent in the personal examination of the skin, women having a greater percentage of lower limbs melanomas which are associated with a better prognosis and immune gender differences.